1. Field of Invention
The invention relates generally to the determination of compass heading through the sensing of Earth's magnetic field, and more particularly to a method and an apparatus for use in magnetic compasses for the characterization of compass magnetic environment and compensation of the heading indications to account for local magnetic distortions.
2. Cross-Reference to Related Documents
The present invention is related in part to U.S. Pat. No. 4,851,775 entitled Digital Compass and Magnetometer Having A Sensor Coil Wound on a High Permeability Isotropic Core issued to Kim, et al. on Jul. 25, 1989, to U.S. Pat. No. 5,239,264 entitled Zero-Offset Magnetometer Having Coil and Core Sensor Controlling Period of an Oscillator Circuit issued to Timothy J. Hawks on Aug. 24, 1993, to U.S. Pat. No. 5,381,603 entitled Reference Pointer For a Compass Display issued on Jan. 17, 1995 to John S. Lee, to U.S. Pat. No. 6,243,660 entitled Digital Compass with Multiple Sensing and Reporting Capability to George Hsu, et al. on Jun. 5, 2001, and to U.S. Pat. No. 6,549,145 entitled Radar/Laser Detection Device with Multi-sensing and Reporting Capability, to George Hsu, et al. Disclosure from these patents is included herein in their entirety by reference.